事实证明Profiling总是必要的...

之前就隐隐约约怀疑自己Server端Resize图片的function可能会有Performance Hit…昨天用Firebug看了一下居然在没有Cache的情况下每次Reload要7秒钟Page才开始Render, 之前都一直在等待Server的Response…被惊到了…原来用的getimagesize();的php function要把图片先下载到server然后才能判断大小, 期间会Block所有Render…所以就在那里活活的wait了7秒钟了…

开始想用JS来做客户端的Resize, 看了一会会jQuery, 决定第二天再写…后来突然想到其实可以直接把图片的大小存在Server端的post-meta…反正要Resize的只有post-image这一张图片…这样每个帖子第一次访问的时候server会访问一下图片, 把大小存下来, 之后其他人的访问就可以直接从数据库读大小, 就是秒间的事了…

改了两分钟搞定, 等待Server response的时间从7秒降到了0.7秒…

改完的代码如下:

	<?php
	function post_image($post, $targetwidth = 100, $targetheight = 100, $resize = true){
	$key="post-image";
	$post_image = get_post_meta($post->ID, $key, true);
	if ($post_image != null) {
	//get image size
	$width = get_post_meta($post->ID, "post-image-width", true);
	$height = get_post_meta($post->ID, "post-image-height", true);
	if ($width == null || $height == null){
	//only calculates the size for the first time.
	list($width, $height, $type, $attr) = getimagesize($post_image);
	if(!update_post_meta($post->ID, "post-image-width", $width))
	add_post_meta($post->ID, "post-image-width", $width, true);
	if(!update_post_meta($post->ID, "post-image-height", $height))
	add_post_meta($post->ID, "post-image-height", $height, true);
	}
	if (!$resize){
	printf ('<img src="%s" height=%d />', $post_image, $targetheight);
	return;
	}
	else if (($width/$height) < ($targetwidth/$targetheight)){
	printf ('<img src="%s" width=%d />', $post_image, $targetwidth);
	}else{
	printf ('<img src="%s" height=%d />', $post_image, $targetheight);
	}
	}
	}
	?>

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